Chelsea fullback Reece James admits they could be playing better.
Asked about their form, the 21-year-old agreed there was room for improvement.
"It's still early on in the season, and we are not going to be at the highest level yet," said James.
"There is still a long way to go. The last few games probably haven't been the highest level from us, but once we start winning and finding form and picking up momentum, I believe our performances will get better.
"Tomorrow is a Champions League game, and the Champions League is a tough competition in football. Anything can happen, so we still need to prepare right. It's not going to be an easy game, they're a good side. Hopefully we can get the win and start building momentum."